Transformer



June 13, 1939. wmz I Reg. 21,116

TRANSFORMER Originai Filed Nov. 10, 1931 I Sheets-Sheet l F4 2. Fig.5.

INVENTOR.

TORNSYS.

' E. WIRZ 'rmusr'o xusn" Jung 13, 1939. Re.'21,11

Original Filed um 10, 1931 '2 Sheets-Sheet 2 .Ja I I I g I I Y, I Jr Y I I ORITJEYSI.

INVENTORY.

. Reissued .Iunel3, 1939 I 1 UNITED STATES PATENT OFFICE TRANSFORMER Emil Wirz, Biel, Switzerland Original No. 2,047,845,

dated July 14, 1936, Se-

rial No. 574,121,- November 10, 1931.. Applica- I tion for reissue June 28, 1938, Serial No. 216,352.

In Switzerland March 17, 1931 u '7 Claims.

through the secondary coil of a transformer in.

. drder to automatically limit the current and/or voltage which is induced in the secondary. coil of the transformer. This prevents the voltage and/or current in the secondary coil from increasing beyond the danger limit, so that the secondary circuit is prevented from being overloaded without the use of automatic safety devices, such as fuses, circuit-breakers, and the secondary coil is therefore protected from burn ing out due to excessive current.

Another object of my invention is to automatically deflect the magnetic flux of the transformer rfrorn the secondary coil, as the secondary current increases.

Another object of my invention is to produce a magnetic leakage between the primary and secondary coils of the transformer, said leakage increasing when the secondary currentincreases,

so that the secondary current and/or voltage cannot increase beyond a determined limit.

Other objects of my invention will be set forth in the following description and drawings which illustrate a preferred embodiment thereof, it being'understood that the above generalv statement -of the objects 'of my invention is intended to generally explain the same and not to limit it in I any manner.

Fig. 1 is-a diagrammatic elevation illustrating myinvention applied to a shell-type transformer, and it illustrates the path of the magnetic leakage, the coils, and the pa h of the magnetic flux when the laminations for securing the magnetic leakage are arranged at the outerfaces of r 40 the iron core and the yokes.

Fig. 2 is a sectional view of Fig. 1, showing the core, the yokes, and laminations for providing the leakage pathof a shell-type transformer, when the leakage path is at the outer faces of the iron core and the'yokes. This view is taken in a median horizontal plane of Fig. 1, and is partially in elevation.

Fig. 3 is a similar section f the core, the yoke, I and 'the laminations for providing the leakage I path of the shell-type transformer, when the laminations for providing the leakage path are partly between the outer faces of the core and the yokes, and partly at the outer faces of the core and the yokes.

Fig. 4 is a diagrammatic elevation of a core type transformer, having a leakage path between the core and the laminations for providing the leakage path, when said. laminations are at the outer faces of the yokes. -,In this figure the 1am- 'inations for providing the leakage path, and

which may be referred to as the "leakage laminations are located at the outer faces of the yokes.

Fig. 5 is a cross-section of the core and the yokes, and the leakage laminations of the coretype transformer, when the leakage 'laminations are located only at the outer faces of the yokes.

This is also a horizontal sectional view, partially in elevation.

Fig.6 is a similar cross-section of the core, the yokes and the leakage laminations of the core-type transformer, 'when the leakage laminations are partly between the yokes, and partly at the outer faces of the yokes.

Fig.- '7 is a diagrammatic elevation of a shelltype transformer having a divided or splitsecondary coil and a plurality of leakage paths, when theleakage laminations are either entirely 'at the outerfaces of the core of the yokes, or when the leakage laminations .are partially between the core and the yokes and partially at the outer faces of the core and the yokes.

Fig. 8 is a diagrammatic elevation of a coretype transformer having divided coils and corresponding leakage paths, when the leakage laminations are either between the yokes, or located at the outer faces of the yokes.

The shell-type transformer which is designated in the drawings consists of the core k which has the same cross-section for the primary and secondary coils. The transformer also has the yokes i which are madeof stamped or cut transformer laminations b. Two coils are arranged upon the iron core proper in such manner as to have the primary cell Pr on one side, and the secondary coil See on the other side. Stamped or cut laminations for the leakage path St are arranged perpendicular to the core, and these leakage laminations are located above and below (at the outer faces of) the yokes and the core.

If an alternating voltage is imposed upon the primary coil, this produces an alternating flux tl and'this primary flux is mainly linked with the part of the iron core which is associated with the secondary coil and with the yokes. Hence this creates a small leakageflux under even a condition of no-load through the leakage path St, and this leakage flux corresponds to thecross-section of the leakage path.

' If the secondary coil is loaded up to a condition of short-circuit, the current flow through the ampere-turns ment the yokes flux into the magnetic circuit of the leakage path so that the proportion of the magnetic flux 4:12 in the secondary coil, with relation to the leakage flux cs is in inverse proportion to the reluctance of both of these by-paths,'and the number of I is the same in both circuits. Hence the secondary current can also increase until a stable or non-changing condition is reached. Hence by a suitable choice of the cross-section of the leakage path and of .the path of the magnetic flux, as well as by arranging the leakage laminations above, below and between the core and .the yokes, any desired limit of the amountof the secondary current can be secured when the secondary. circuit is short-circuited. this arrangecan also be simultaneously enlarged or reinforced, according to the arrangement of the 'leakage-laminations, so that the noload current and the no-load loss are decreased, which is a very important advantage in the use of small transformers.

This arrangement of the leakage path, in order to reduce the short-circuit current, can be practically-utilizecl in all transformers of the shelltype of any capacity. However, whenthecapacity of the transformer increases, it is necessary to divide the coils; so that a pair of leakage paths, or a plurality of pairs of correspondingly provided, as shown in Fig. 7.

The core-type transformer which is designated consists of a pair of cut or stamped cores k, and the side yokes i, which are made of t laminations b. The primary coil Pr is located on age laminations above or reduction of the secondary current this 1 cs when the secondarycircuit has-its load increased up to a condition of short-circuit so that one iron core, and the secondary coil Sec is arranged upon the other core.

In core-type transformers, the'leakage laminations can be inserted'into the yokes, or said yokes can be provided withleakage lamination projections V. Hence the cross-section of the leakage pathor core can consist of'leakage laminations which'are arranged either above orbelow or between the yokes. In this type oftransformer, when the loadis increased up to shortcircuit, the current flow through the secondary coil also by-passes apart of the primary flux from the secondary coil to the leakage path.

When there is no load upon thetransformer, a leakage flux no is produced which depends upon the cross-section of the leakage path, and p e flux increases up'to a mazdmum value secondary circuit under a condition of short-circuit can be reduced to the decan be secured is therefore predetermined by a suitable choice of the cross-section of the magnetic leakage Path and also by locating the leakbelow or between the the no-load current and which is produced by jections.

This cut of dition of short-circuit can be all core-type transformers of ever, in one of he coils in the extends practically used in anycapacity. How

21,116 a portion of the primary leakage paths must be transformer the leakage paths for the under a conincreased capacity adlvislon of thrc unmanberswhicn.

are laterally located behind the. core and also in front" of the core. Said leakage path members can be considered as constituting lateral enlargements of the core. tends through members which are laterally lo;- cated in front of the yokes and also behind the yokes, thus constituting .in efiectv lateral enlargements of the. yokes.

follows Assuming 'that the secondarycurrent can suddenly increased due to the formation of a short circuit, thiscauses a correspondlnglyrapid Likewise, the leakage path ex-fl These'j leakage path meinbets are located above and below the iron corev increase in the flux which is producedby the secondary current in the secondary coil (or coils). This sharp increase in the magnetic flux which is linked with the secondary coil, tends to repel the passageof the primary flux through the secondary coil, so that theprimary coil will be bypassed through the leaking means, which constitute a leakage path. 1

In Figs. 3' and-6, the leakage means is shown as provided in two. places, each being of a different type. One type of meansis depicted at St,

and comprises-laminations with integral leakage" flux bridges added at the outer faces to the core laminations forming enlargements of the yokes i, I

the other being depicted as small magnetic bridges or shunt members Sh inserted between the core and yokes, one on each side and disposed at intermediate points between the outer faces ,of 'the core and yokes. In order to attain the eilect of a leakage path free from any air-gaps and having relatively sniall'reluctances at all points of the path for the latter type as well as for the former, the members Sh are'mortised into the yokes and/or the core. This imparts additionally the mechanical advantage of insuring against lateral displacement of themembers Sh. The invention in this form is notto be limited to means, the use of the latter contemplated.

I have shown a preferred embodiment of my type alone being'also invention, but it is clear that numerous changes and omissions could be made without departing from its spirit. v

The improved transformer can be used in alarm systems,v in arm uncement systems, and in rectlflers;

As shown in the drawings, the leakage means are of smaller effective cross .section'than the permeable means through which'the primary 1 flux and the'secondary flux pass.

Having described nrv invention, what I claim asnew and desire to secure by Letters Patent is: i

1. A transformer having. core means and yoke means, a primary coil and a cated on said cone means, anda-leakage bridge under maximum predetermined load.v

2. A transformer having a laminated core means, a primary coil and a secondary coil located on said core means, said core means having additional laminations which form a leakage bridge which is adapted to bypass only a. portion of the main flux of the primary coil, said leakagebridge forming a fixed and wholly closed leakage path which is wholly free from any leakage air gap with relation to said core means, the eifective cross section of said leakage bridge being less than the effective cross section of said core means, the leakage bridge having suflicient cross-section to limit the flux'through said secondary coil automatically and without the formation of an air-gap, under maximum predetermined load.

3. A transformer having a yoke means and laminated core means, a primary coil and a sec+ ,ondary coil located on said core means, said core means having'additional laminations which form a leakage bridge which is adapted to bypass only a portion of. the main flux of the primary coil, said leakage bridge forming a fixed and wholly closed leakage path which is wholly free from any leakage air gap with relation to said core means, the effective cross section-of said leakage bridge being less than the effective cross section of said core means, said leakage bridge constituting a fixed and :continuous enlargement of the yoke means of the transformer, the yeakage bridge having sufficient cross-section to limit the flux through said secondary coil automatically and without the formationfof an air-gap, under maximum predetermined load.

4. A transformer having a yoke means and laminated core means, a primary coil and a secondary coil located on said core means, said core means having additional laminations which form a leakage bridge which is adapted tobypass only a portion of the main1lnx of the primary coil, said leakage bridge forming a fixed and closed leakage path which is wholly free from any leakage air gap with relation to said core means.

the eifective cross section of said leakage bridge being less than the effective cross section of said core means, said leakage bridge constituting a fixed and continuous enlargement of the yoke of the transformer, some of the laminations of the leakage bridge being locatedbetween the core means and the yoke means, and some of said laminations of the leakage bridge being located 'ing space.

said yoke means, the leakage bridge having suflicient cross-section to limit the flux through said secondary coil automatically and without the formation of an air-gap, under maximum predetermined load.

5. A transformer comprising an iron body of the shell type consisting of assembled laminations providing yokes and an interior core, windings on said core, and leakage control means associated with said iron body and provided in-two forms, one of which consists of additional laminations provided with integral leakage bridging members disposed transversely to the core at an intermediate point, said additional laminations providing'enlargements of the yokes, said other form consisting of magnetic shunt members inserted between the core and side yokes and having at least one end mortised into place thereby providing tight butt jointsof relatively low reluctances and mechanical stability.

6. A transformer having aniron body of the shell type and consisting of assembled laminations providing yokes and an interior core, windings on said core, andleakage control bridging means associated with said iron body and consisting of additional laminations superposed upon the faces of the core laminations and having integral bridging members extending thereacross transversely of the core at an intermediate point.

'7. A transformer having an iron body of the shell type and consisting of assembled laminaat the outer faces of said core means andof tions providing yokes and an interior core, said laminations comprising an interior group having their core and yoke portions notched to provide;'

at least one pair of oppositely disposed recesses, the exterior groups being without such notches, windings on said core. and magnetic leakage control means consisting of magnetic members of lengths greater than the distance from core to a side yoke and of an average cross-section materially less than that of the core tightly inserted in said recesses between a core and an opposite side yoke and having its ends forming a mortlsed joint with said notched laminations whereby a relatively small magnetic reluctance obtains at the joint and also. the. mechanical advantage of insuring against lateral displacement in the wind- EMILWIRZ. 

